SHAFAQNA – Berkeley, Missouri: Demonstrators hoping to block Interstate 70 here on Wednesday to protest the shooting death of Michael Brown a month ago were barred by the police from entering the highway. About 20 protesters were arrested when they sat down in the road near an entrance ramp.

As traffic continued to move freely during the late-afternoon rush, about 100 demonstrators and 100 police officers, some in riot gear, faced each other near the eastbound on-and-off ramps at Hanley Road, not far from the airport. Officers warned protesters that if they entered the road they would be arrested.

One demonstrator, Charles Brooks, was among those who sat down in the road, shouting, “McCulloch got to go. McCulloch got to go,” a reference to the St. Louis County prosecutor whose office is investigating the shooting. Asked why he had joined the protest, he said, “I want to see justice served here.”

Seconds later was picked up by a police officer, handcuffed and led to a bus from the Missouri Department of Corrections.

Although the demonstration, which formed shortly after 3 p.m., was generally peaceful, some objects were hurled at the police, who chased down some of those who had thrown things, and arrested them.

The demonstration took place about five miles from Ferguson, Missouri, where Brown, a black teenager who was unarmed, was killed by a white Ferguson police officer, Darren Wilson, on Aug. 9. Some witnesses have said Brown had put his hands up in surrender. Wilson, who has not been charged, has not been seen in public since.

The demonstration was meant to last 4 1/2 hours, symbolizing the death of Brown, whose body lay on the street for that length of time after he was shot, after an apparent scuffle with the officer.

Organizers had hoped to pressure Gov. Jay Nixon to appoint a special prosecutor to lead the investigation of the killing. Activists and black lawmakers say McCulloch has shown bias in favor of law enforcement in previous police shooting cases and they question his impartiality. His father was a police officer who was shot and killed by a black man when McCulloch was 12, and his mother and other relatives worked for decades for the St. Louis Police Department.

But last week, Nixon appeared to have stripped himself of the power to remove McCulloch, after he lifted the executive order that established a state of emergency in Ferguson. McCulloch has said he would not make a decision to arrest Wilson himself but would instead present evidence to a grand jury.

The rallying point for protesters – a parking lot near the intersection of I-70 and North Hanley Road – was near the former site of a fast-food restaurant where two unarmed black men suspected of dealing drugs were shot and killed by undercover officers in 2000. The white officers said they feared being run over by the car the men occupied, and McCulloch brought no charges against them.

Some black leaders were skeptical that interrupting the commute for thousands of motorists who have no say in the case would help their cause and declined to participate, including representatives of the NAACP and the Rev. Al Sharpton’s National Action Network. But organizers of the blockade said disrupting people’s day was a “small sacrifice” for seeking justice for Brown.

“Civil disobedience does cause inconvenience,” said Eric E. Vickers, a lead organizer who is the chief of staff for state Sen. Jamilah Nasheed, D-St. Louis. “It does cause discomfort. All your pleas are made to do the right thing, and when someone doesn’t do the right thing then the person has to be willing to sacrifice themselves by being jailed, in order to have that right result achieved.”

The highway shutdown was organized by some of the same black activists who blocked four lanes of I-70 in July 1999 in a demonstration that brought traffic to a standstill for more than an hour and led to the arrests of Sharpton and more than 100 others. The organizers of the Wednesday demonstration said that protesters would conduct themselves in a peaceful and orderly manner, but criticized law enforcement officials after a meeting on Monday with the authorities.

Protesters were planning to use some of the same tactics they used in 1999 to get their supporters physically onto the highway. In that protest, some demonstrators were on foot and others were in vehicles. Those in cars drove onto the highway, formed a line with their vehicles and stopped at a coordinated time and place. Those on foot, who had assembled nearby and had blocked traffic at the entrance ramps, walked down the ramps and sat down on the interstate as their supporters in cars who had stopped traffic sped away.

“Frankly, we feel very confident about our ability to shut down any highway in America,” Vickers said earlier in the week. He has threatened or carried out other traffic shutdowns in the St. Louis area since 1999. “If you’ve got enough cars and people organized, it’s almost impossible to stop.”

In 1999, protesters were calling for more highway construction jobs for black workers and contractors. On the eve of a second planned traffic blockade, state officials largely met their demands, creating a minority training program within the Missouri Department of Transportation that has helped about 300 men and women get construction jobs.